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This study presents a novel design that combines cooling tower (CT) and traditional solar chimney power plant (SCPP) technologies for electricity generation and seawater desalination. The proposed hybrid solar chimney power plant (HSCPP) shares the operation of the chimney part and the bi-directional turbine between the SCPP and CT, allowing alternative operation of the CT during the nighttime and the SCPP during the daytime, and achieving continuous system utilization. The performance of the HSCPP design was validated against baseline models using 1 year of weather data from the city of Aqaba in Jordan. Results revealed that the HSCPP has the potential to produce ~50% electricity (528 MWh/year) higher than the traditional SCPP (365 MWh/year). The annual seawater desalination capacity of the HSCPP was estimated at 138300 m3, which is 1.5 folds higher than the traditional SCPP. The HSCPP reduced the annual CO2 emissions by 40% (~500 tons) compared to traditional SCPP with annual revenue of US$190 000. Furthermore, the results show that the HSCPP is 1.4 times more efficient than the traditional SCPP. The HSCPP achieved a system utilization factor of 0.73% compared to 0.52% for the traditional SCPP. The HSCPP showed promising sustainable and economical technology for the production of electricity and water while reducing the emission of GHG. Scopus

Summary There are many low-temperature heat sources; however, current technologies for their utilization have a relatively low efficiency and high cost. The leading technology in the low-temperature domain for heat-to-work conversion is the organic Rankine cycle (ORC). Absorption power cycles (APCs) are a second option. Nearly all currently known APCs, most importantly the Kalina cycle, use a water-ammonia mixture as their working fluids. This paper offers a theoretical exploration of the possibility of utilizing aqueous solutions of three salts (lithium bromide, lithium chloride and calcium chloride), known mainly from absorption cooling, as working fluids for APCs. The cycles are compared with a typical steam Rankine cycle, a water-ammonia APC, and (subcritical) ORCs with a range of working fluids explored. The analysis includes a parasitic load for heat rejection by a cooling tower or air-cooled condenser. The absorption cycles exhibit better performance than all Rankine-based cycles analysed in temperatures below 120°C. For the LiBr-based APC, a detailed thermal design of the cycle is provided for 100°C water as a heat source and a sensitivity analysis is performed of the parameters controlling the main cycle. Mechanical design considerations should not pose a problem for small power units, especially in the case of expansion machines, which are often problematic in ORCs. The salt-based APCs also carry environmental benefits, as the salts utilized in the working fluids are non-toxic. Copyright © 2016 John Wiley & Sons, Ltd.

SUMMARY GTHTR300A is a power plant design based on high-temperature gas-cooled reactor. It relies on exclusive dry cooling for production and in emergency, a practice not found in existing and other proposed plants. Besides well-known environmental benefits, successful use of dry cooling may provide the new found safety advantage because it avoids water-related event such as tsunami or generation of explosive hydrogen. In the GTHTR300A, the reactor coolant is used to drive a direct-cycle gas turbine, and further dry systems are provided to meet the three general cooling requirements. The system to reject power generation waste heat couples the reactor and a natural draft air cooling tower by a closed helium circulation loop. Careful design and operational measures are introduced to ensure the viability of economics, which proves difficult in existing plants. Separately, a natural convective air system is used to remove core decay heat in emergency. Detailed simulation shows that the system placed outside the reactor can maintain the temperatures of reactor fuel and structure below design limits even in case of simultaneous loss of coolant and station blackout. Finally, the study shows that the spent fuel may be stored in dry wells and safely cooled by natural convective air. By reliance on economic and safe dry cooling, the design succeeds in making inland construction feasible even without source of cooling water, and the resulting benefit to safety and environment is compelling in light of the 2011 Fukushima accident due to tsunami. Copyright © 2014 John Wiley & Sons, Ltd.

SUMMARY In this paper, the mathematical modeling and simulations of a concentrating solar power system located at the Middle East Technical University Northern Cyprus Campus are presented. The system consists of parabolic trough collectors (PTCs), a propane boiler, an organic Rankine cycle (ORC), and a wet cooling tower. Presently, the PTC field is severely undersized with respect to the ORC making the system impossible to operate without burning significant propane. Expanding the solar field could result in better system performance. Hourly, daily and seasonal variations in the performance of this system are simulated using hourly meteorological data for Larnaca, Cyprus, over an entire year. Because the ORC is driven using a relatively low-temperature heat source rather than PTCs, the usage of nonconcentrating evacuated tube collectors that collect both beam and diffuse radiation is explored. The performance of east–west and north–south–tracking axis PTCs and the entire inventory of nonconcentrating evacuated tube collectors that were rated by the Solar Rating and Certification Corporation are compared in terms of annual performance metrics. Based on the simulations, several nonconcentrating evacuated tube collectors are identified with better thermal performance than PTCs, and the feasibility of using these collectors should be explored further. Copyright © 2013 John Wiley & Sons, Ltd.

SUMMARY This paper presents a flash cooling desalination system to reduce thermal pollution and also to produce freshwater using the heat rejected by the process plant into the environment. The prototype plant was erected in an existing coal-based thermal power plant at North Chennai, India. It consists of an air-tight barometric sealed flash cooler, positioned at a level at least 10.13 m above the ground level, for the feed seawater to flow under the effect of gravity and to maintain a low pressure. The prototype plant was tested by using a small fraction of the available flows without using any mechanical energy such as motive steam from the power plant. A freshwater production rate of 0.49% of the feed seawater is obtained from the available thermal gradient of 8.5 °C from the condenser reject heat of the power plant, and then the waste water is discharged at near intake concentration of salinity into the sea. The temperature of hot feed seawater is also reduced by 3 °C. The results are used to provide an outline technical specification for larger capacity desalination plant to meet the growing need for freshwater. This is an environment friendly desalination process and consumes no chemicals as it operates at near ambient temperature. This can be effectively utilized for the generation of freshwater, besides protecting the marine ecosystem along the shore, and reducing the load on the cooling tower or eliminating the need for it completely. Copyright © 2012 John Wiley & Sons, Ltd.

Re-circulating cooling water systems offer the means to remove heat from a wide variety of industrial processes that generate excess heat. Such systems consist of a cooling tower and a heat-exchanger network that conventionally has a parallel configuration. However, reuse of water between different cooling duties allows cooling water networks to be designed in a series arrangement. This results in performance improvement and increased cooling tower capacity. In addition, by the integration of ozone treatment into the cooling tower, the cycle of concentration can be increased. The ozone treatment also dramatically reduces the blow-down that, in turn, is environmentally constructive. In this study, a new environmental-friendly and cost-effective design methodology for cooling water systems was introduced. Using this design methodology, Integrated Ozone Treatment Cooling System (IOTCS), achievement of minimum environmental impacts and total cost were afforded through a simultaneous integration of the cooling system components using an ozone treatment cooling tower and optimum heat-exchanger network configuration. Moreover, in the proposed method, the cooling tower optimum design was achieved through a mathematical model. The IOTCS design method is based upon a complex design approach using a combined pinch analysis and mathematical programming that provides an optimum heat-exchanger configuration while maximizing water and energy conservation and minimizing total cost. Related coding in MATLAB version 7.3 was used for the illustrative example to obtain optimal values in the IOTCS design method computations. The results of the recently introduced design methodology were compared with the conventional method. Copyright © 2009 John Wiley & Sons, Ltd.

A strategy of fault detection and diagnosis (FDD) for HVAC sub-systems at the system level is presented in this paper. In the strategy, performance indices (PIs) are proposed to indicate the health condition of different sub-systems including cooling tower system, chiller system, secondary pump systems before heat exchangers, heat exchanger system and secondary pump system after heat exchangers. The regression models are used to estimate the PIs as benchmarks for comparison with monitored PIs. The online adaptive threshold determined by training data and monitored data is used to determine whether the PI residuals between the estimation and calculation or monitoring are in the normal working range. A dynamic simulation platform is used to simulate the faults of different sub-systems and generate data for training and validation. The proposed FDD strategy is validated using the simulation data and proven to be effective in the FDD of heating, ventilating and air-conditioning (HVAC) sub-systems. Copyright © 2009 John Wiley & Sons, Ltd.

This study attempts to quantify the potential improvement in a natural draft wet cooling tower (NDWCT) performance that can be attained by optimizing the fill and water distribution profiles across the tower and to provide designers with the modelling tools for such an investigation. A simple two-dimensional (2D) model is described, which allows rapid evaluation of NDWCT performance for use with an optimization procedure. This model has been coupled with an evolutionary optimization algorithm to determine the optimal fill shape and water distribution profile to maximize the cooling range of a typical NDWCT. The results are compared against a 2D axisymmetric numerical model. The extended 1D model is found to significantly reduce computational time compared with the numerical model, allowing a wide range of parameters to be tested rapidly with reasonable accuracy. The results show that the optimal layout differs significantly from a uniform profile, with both the water flow rate and the fill depth decreasing towards the centre of the tower where the air is warmer with reduced cooling potential. The overall improvement in the tower cooling range is very low under the design conditions tested, due largely to the highly coupled nature of the airflow and heat transfer in the tower. It is concluded that any design modifications of the type considered would need to be carefully optimized to have any possibility of improving performance. Copyright © 2008 John Wiley & Sons, Ltd.

This paper presents a case study of the prediction, potential and control of plume in wet cooling towers from a huge commercial building in Hong Kong based on the weather data available for a particular year. The power input is found to be lower and the coefficient of performance (COP) moderate when all the 10 towers with low speed are in use, while it is found to be reverse when there are five towers, especially, three low and two high-speed towers are used. It is also found that the combined heating and cooling option can be a better approach than that of the heating option alone from the point of view of thermodynamics as well as from the point of view of economics. The COP of the chillers increases from 6.01 to 7.09 when the number of cooling towers increases from five to ten. On the other hand, the power consumption first decreases and then increases which is mainly due to the increment in the consumption of fan power from 270 to 900 kW for both options. The overall power consumption decreases slightly for the combined heating and cooling option, while in the heating option, the overall power consumption increases slightly. However, it is observed that a proper operation of cooling towers is an effective means to control and/or at least reduce the potential of visible plume generated by wet cooling towers at the existing chilling plant design for this particular building. Copyright © 2006 John Wiley & Sons, Ltd.

An analytical model was developed to describe thermodynamically the water evaporation process inside a counter-flow wet cooling tower, where the air stream is in direct contact with the falling water, based on the implementation of the energy and mass balance between air and water stream describing thus, the rate of change of air temperature, humidity ratio, water temperature and evaporated water mass along tower height. The reliability of model predictions was ensured by comparisons made with pertinent experimental data, which were obtained from the literature. The paper elaborated the effect of atmospheric conditions, water mass flow rate and water inlet temperature on the variation of the thermodynamic properties of moist air inside the cooling tower and on its thermal performance characteristics. The analysis of the theoretical results revealed that the thermal performance of the cooling tower is sensitive to the degree of saturation of inlet air. Hence, the cooling capacity of the cooling tower increases with decreasing inlet air wet bulb temperature whereas the overall water temperature fall is curtailed with increasing water to air mass ratio. The change of inlet water temperature does not affect seriously the thermal behaviour of the cooling tower. Copyright © 2005 John Wiley & Sons, Ltd.

The thermal performance of a natural draft dry cooling tower (NDDCT) under a crosswind has been investigated using a general-purpose CFD code. A three-dimensional study using the standard k-e turbulence model to simulate airflow in and around an NDDCT has been conducted. A parametric study has been carried out to examine the effect of crosswind velocity profile and air dry-bulb temperature on the thermal performance of an NDDCT. Two approaches have been considered in this study to quantify the crosswind effect. Firstly, simulations have been conducted at the nominal conditions and crosswind effect has been represented by thermal effectiveness parameter. Secondly, the ejected heat from the NDDCT has been maintained at a constant value (285 MW) and the crosswind effect has been represented by the change in the cooling tower approach parameter. After quantifying the effect of the crosswind on the thermal performance, windbreak walls have been introduced as a means of reducing this effect. The results in this paper show the importance of considering the crosswind velocity profile. Moreover, the introduction of windbreak walls has indicated an improvement in reducing the thermal performance losses due to the crosswind.

Simplified analytical models are developed for evaluating the thermal performance of closed-wet cooling towers (CWCTs) for use with chilled ceilings in cooling of buildings. Two methods of simplification are used with regard to the temperature of spray water inside the tower. The results obtained from these models for a prototype cooling tower are very close to experimental measurements. The thermal performance of the cooling tower is evaluated under nominal conditions. The results show that the maximum difference in the calculated cooling water heat or air sensible heat between the two simplified methods and a general computational model is less than 3%. The analytical model distribution of the sensible heat along the tower is then incorporated with computational fluid dynamics (CFD) to assess the thermal performance of the tower. It is found that CFD results agree well with the analytical results when the air flow is simulated with air supply from the bottom of the tower, which represents a uniform air flow. CFD shows the importance of the uniform distribution of air and spray water to achieve optimum design. Copyright © 2002 John Wiley & Sons, Ltd.

A closed wet cooling tower, adapted for use with chilled ceilings in buildings, was tested experimentally. The thermal efficiency of the cooling tower was measured for different air flow rates, water flow rates, spray flow rates and wet bulb air temperatures. CFD was also used to predict the thermal performance of the cooling tower. Good agreement was obtained between CFD prediction and experimental measurement. Copyright © 2000 John Wiley & Sons, Ltd.

This paper reports on a feasibility study of a solar-powered heating/cooling system for a swimming pool/space combination in a tropical environment. The system utilizes an absorption chiller and a cooling tower to meet the facilities and locker room load. The heating is accomplished by employing hot water generated by heat exchange with the solar collector working fluid. Two thermal storage tanks were employed for the collector and domestic use. The absorption chiller utilizes hot water to regenerate the LiBr solution. The proposed system enables the swimming season to be extended from sixteen weeks to fifty-two weeks. Simulation results indicate that a combination of a double glazed collector area of 600–4800 m2 and a storage tank volume of 11·36 m3 results in a 25–37% reduction in the consumption of natural gas. Economic analysis is performed based on the life-cycle-cost method and takes into account the effects of discount rate, fuel price and fuel inflation rate. Different scenarios for which the solar-assisted system is economical are presented and analysed. © 1997 John Wiley & Sons, Ltd.

A simplified steady-state model has been developed to describe thermodynamically the operation of a centralized cooling system. This model resolves the mass and energy equations simultaneously and uses inputs that are readily available to the design engineer. The model utilizes an empirical relationship for the compressor power as a function of cooling load and key temperatures. The outputs include the chiller coefficient of performance (COP) and the compressor actual power. The model simulation results are validated with a manufacturer performance data and compared with the experimental data collected at Hewlett-Packard Laboratories site for two chillers: a variable speed and a constant speed chiller. The results of the model are found to closely match the current experimental data with less than 5% average deviation for chiller load over 10% and with a maximum deviation of 18% at 95% chiller load. For the constant speed chiller, the chiller efficiency increases with increasing load and peaks at full load. For the variable speed chiller, the chiller efficiency peaks at part loading between 40 and 80% of the chiller full load depending on the condenser water temperature. This indicates that for variable speed chillers, the chiller design has been optimized for loading less than 100% depending on the ambient conditions, customer specifications and size of the chiller. Copyright © 2010 John Wiley & Sons, Ltd.

The thermal performance of a building fitted with an evaporative cooling tower has been evaluated in terms of discomfort index for two climates, namely, composite and hot-dry, typified by New Delhi and Jodhpur, respectively. The effects of various evaporative cooling parameters (height and cross-sectional area of the tower, packing factor, area of the pads, resistance offered to the air flow and local wind conditions) on the performance of the building have been analysed. It was found that, for given parameters of the tower and wind conditions, there is an optimum height of the tower for which the thermal discomfort condition in the building is minimum. The optimum values of the tower height for comfort conditions in the building for various other tower parameters have been obtained for each climate.

This paper presents a parametric study of an evaporating cooling tower to investigate the effect of different tower parameters on the cooling potential of the tower connected to a room. The effect of the environmental conditions on the cooling potential of the tower is investigated by estimating its cooling potential in different months for two climates, namely hot-dry and composite, typified by Jodhpur and Dehli, respectively.

The paper reports on a feasibility study of a solar-powered heating/cooling system for a swimming pool/space combination in a tropical environment. The system employs an absorption chiller and a cooling tower to meet the locker-room load. The heating is accomplished by employing hot water generated by heat exchange with the solar collector working fluid. Two thermal storage tanks are employed for the collector and domestic use. The absorption chiller utilizes hot water to regenerate the LiBr solution. The proposed system will enable the swimming season to be extended from 16 weeks to 52 weeks. The economic analysis is performed based on the life-cycle-cost method. The effects of discount rate, fuel prices, and the fuel inflation rate are discussed. The analysis shows, with the present level of fuel prices, that the solarassisted system is not economical enough over a life cycle of 10 years. The study presents different scenarios for which the solar-assisted system is, however, economical.

Etude experimentale d'une tour de refroidissement a triage force fonctionnant a contre-courant en utilisant la technique de reponse a une impulsion pratiquee sur l'entree d'eau et sur l'entree d'air. Presentation d'un modele mathematique du coefficient global de transfert de chaleur qui tient compte du coefficient de dispersion axiale cote air et cote eau. Comparaison des resultats calcules et ceux obtenus a des donnees experimentales

A dynamic method is used to predict the liquid axial dispersion coefficient in cooling towers. A KCl tracer was employed on the water inlet on the top of the tower. Input and response signals were measured. Cooling tower parameters were determined by predicting the response tracer signal and curve fitting technique in the time domain.